A portable electronic device such as a mobile phone, PHS (Personal Handy-phone System), PDA (Personal Digital Assistant), and small-sized personal computer is widely used.
In these portable electronic devices, there is a tendency that power consumption increases due to addition of various new functions and/or improvement of processing speed of a CPU (Central Processing Unit).
A secondary battery, owing to its improvement in performance, now have a longer life compared with before. However, according to such a circumstance in which a communication function continues to be used for a long time, the battery reaches exhaustion in a comparatively short time, for example, in one day. Once the battery reaches exhaustion, all functions of a portable electronic device become disabled.
In such a case, conventionally, if a consent for utility power or a cigar lighter socket of an automobile is available in a near place, a user approaches the place to connect an exclusive battery charger to the exhausted battery in order to charge the battery. Moreover, by ordinarily carrying a standby battery already charged and by replacing the exhausted battery with the standby battery, the trouble of battery exhaustion can be resolved.
However, a user does not always carry the exclusive battery charger or standby battery already charged. Though a device to feed power by housing a dry battery into a specified battery case and connecting the dry battery to a power terminal of a portable electronic device and a battery charger equipped with a hand handle or solar battery are available, unless the user always carry these battery chargers, it is impossible to resolve the trouble of battery exhaustion.
When the battery reaches exhaustion outdoors, if there is luckily a convenience store or an electrical appliance in a near place, a user can buy a disposable battery charger or a set of a battery case or battery in some cases. The products for saving an immediate situation are comparatively expensive and go to waste in the end. Moreover, if energy exhaustion occurs in a state where a user cannot charge a battery due to a large-scale disaster such as an earthquake or during mountain climbing, a user cannot buy such products, thus making it impossible to utilize the advantage of a user's possessing a mobile phone for communications in the case of emergency.
As described above, mobile phones for themselves ideally have a careful measure against the occurrence of the battery exhaustion from a viewpoint of prevention against disasters.
To solve this problem, a first proposal is disclosed (for example, Patent Reference 1) in which a spiral spring is mounted internally in a drum around which a thread is wound to rotate an electricity generation rotor to obtain power. According to the first proposal, by using a spiral spring, an operation to put threads in a reciprocating motion is repeated and the drum rotates when the thread moves in one direction. The rotation of the drum causes a rotor of a power generator which is engaged with a Dobo gear to generate electricity and the battery is charged.
According to the first proposal, the drum rotates during one directional motion out of the reciprocating motions of the thread and, therefore, its rotation becomes intermittent. Accordingly, the produced electrical energy is not allowed to be directly supplied to electrical appliances such as an electronic circuit. To solve this problem, in the first proposal, an output from the power generator is supplied to an battery. As a result, once the battery exhaustion occurs, supply of a considerable amount of electric energy is required to restore an output voltage of a battery to a normal value. To achieve this, it is necessary that the reciprocal motion of the thread is repeated a huge number of times for a long time. For example, a device supplying power generated by further turning a handle by hand and more effectively rotating a rotor of the power generator has been introduced commercially, however, due to the reason similar to the above, the restoration from the occurrence of the energy exhaustion to a battery-usable state is actually difficult.
A mobile phone is disclosed as a second proposal in, for example, Patent Reference 2 in which opening and closing torque of a foldable mobile phone is accumulated in a spiral spring and a string of piezoelectric elements serving as a continuous vibrating source is vibrated. According to the second proposal, every time the foldable mobile phone is opened and closed, rotation torque is accumulated in a spiral spring. The rotation torque continues to apply an up-and-down vibration to an unillustrated string of piezoelectric elements.
Patent Reference 1: Japanese Patent Application Laid-open No. 2001-189152 (Paragraph 0008, Paragraph 0011, FIG. 1)
Patent Reference 2: Japanese Patent Application Laid-open No. 2003-204091 (Paragraphs 0010 to 0014, FIG. 3)